Kitabatake et al., disclose in U.S. Pat. No. 6,270,573 B1, CVD and CVD-related methods of producing silicon carbide substrates, including the growing of silicon carbide film by supplying separate silicon atoms and carbon atoms on a surface. The silicon-carbon bond formation occurs mainly on the surface of the substrate, a step that usually requires high temperatures, in this particular case the required temperature being 1300° C. MBE and MO-CVD may use species that contain a limited number of pre-existing Si—C bonds in the precursor, this number being usually related to precursor synthesis requirements.
Kong et al. (European Patent No. EP 0,970,267) describe a susceptor design for silicon carbide resulting in minimizing or eliminating thermal gradients between the two surfaces of a substrate wafer. The CVD and CVD-related deposition procedures of Kong et al., require strict control of the temperature field and the gas flow at the surface of the substrate, where the Si—C bond formation is occurring.
Grigoriev et al. (Grigoriev, D. A., Edirisinghe, M. J., Bao, X., Evans, J. R. G. and Luklinska, Z. B.(2001) “Preparation of silicon carbide by electrospraying of a polymeric precursor,” Philosophical Magazine Letters (UK), 81, 4, 2001 by Dept. of Mater., Queen Mary Univ. of London, UK) present silicon carbide coatings and films prepared for the first time by electrostatic atomization of a solution of a polymeric precursor and deposition onto alumina and zirconia substrates. In the method of Grigoriev et al., the polymeric source already contains most of the Si—C bonds required for the formation of the SiC film; however, the molecular source is carried to the surface inside cages of solvent molecules, implicitly leading to contamination of the film, shrinking and outgassing phenomena, due to solvent evaporation and polymer cracking. These effects will be present in any polymer-assisted method (spin-coating, spraying, laser ablation . . . ).
Lau et al. (Lau, S. P., Xu, X. L., Shi, J. R., Ding, X. Z., Sun, Z. and Tay, B. K. (2001) “Dependences of amorphous structure on bias voltage and annealing in silicon-carbon alloys,” Materials Science & Engineering, B85 (16), Sch. of Electr. & Electron. Eng., Nanyang Technol. Inst., Singapore) report on amorphous silicon-carbon alloy films that have been obtained by filtered cathodic vacuum arc (FCVA) technique. They have observed that the disorder of the Si—C network increased with using the high bias voltages during the deposition. This high disorder in the film with high bias voltages induces the smaller nanometer crystallites after annealing at 1000° C. rather than low bias. The Raman peaks shift to the high frequency with increasing the annealing temperature up to 750° C. due to the increase of nanometer grain size at the same bias. A sharp transition from nanocrystalline to polycrystalline can be observed when the films are annealed under 1000° C.
Jana of al. (Jana, T., Dasgupta, A. and Ray, S. (2001) “Doping of p-type microcrystalline silicon carbon alloy films by the very high frequency plasma-enhanced chemical vapor deposition technique” Journal of Materials Research, 16(7) 2001, 2130-5, Energy Res. Unit, Indian Assoc. for the Cultivation of Sci., Calcutta, India) present the synthesis of p-type silicon-carbon alloy thin films by very high frequency plasma-enhanced chemical vapor deposition technique using a SiH4, H2, CH4, and B2H6 gas mixture at low power (55 mW/cm2) and low substrate temperatures (150-250° C.). Effects of substrate temperature and plasma excitation frequency on the optoelectronic and structural properties of the films were studied. A film with conductivity 5.75 Scm−1 and 1.93 eV optical gap E04 was obtained at a low substrate temperature of 200° C. using 63.75 MHz plasma frequency. The crystalline volume fractions of the films were estimated from the Raman spectra. They observed that crystallinity in silicon carbon alloy films depends critically on plasma excitation frequency. When higher power (117 mW/cm2) at 180° C. with 66 MHz frequency was applied, the deposition rate of the film increased to 5.07 nm/min without any significant change in optoelectronic properties.
Yamamoto et al. (Yamamoto et al., Diam. Relat. Mater., vol. 10 (no. 9-10), 2001, pp. 1921-6) present a doping procedure whereby amorphous SiCN films were prepared on Si (100) substrates by nitrogen ion-assisted pulsed-laser ablation of a SiC target. The dependence of the formed chemical bonds in the films on nitrogen ion energy and the substrate temperature was investigated by X-ray photoelectron spectroscopy (XPS). The fractions of sp2 C—C, sp3 C—C and sp2 C—N bonds decreased, and that of N—Si bonds increased when the nitrogen ion energy was increased without heating during the film preparation.
The fraction of sp C—N bonds was not changed by the nitrogen ion irradiation below 200 eV. Si atoms displaced carbon atoms in the films and the sp3 bonding network was made between carbon and silicon through nitrogen. This tendency was remarkable in the films prepared under substrate heating, and the fraction of sp3 C—N bonds also decreased when the nitrogen ion energy was increased. Under the impact of high-energy ions or substrate heating the films consisted of sp2 C—C bonds and Si—N bonds, and the formation of Sp3 C—N bonds was difficult. The Yamamoto procedure proposes a doping step separate from the synthesis step.
Budaguan et al. (Budaguan, B. G.; Sherchenkov, A. A.; Gorbulin, G. L.; Chernomordic, V. D. (2001) “The development of a high rate technology for wide-bandgap photosensitive a-SiC:H alloys,” Journal of Alloys and Compounds, 327(30) Aug., 146-50, Inst. of Electron Technol., Moscow, Russia) discuss in their paper the deposition process and the properties of a-SiC:H alloy fabricated for the first time by 55 kHz PECVD. It was found that 55 kHz PECVD allows an increase in the deposition rate of a-SiC:H films.
Modiano et al. (Japanese patent No. 145138/95) present a process for producing silicon carbide fibers having a C/Si molar ratio from 0.85 to 1.39, comprising the steps of rendering infusible the precursory fibers made from an organosilicon polymer compound, then primarily baking the infusible fibers in a hydrogen gas-containing atmosphere. This process for producing silicon carbide thin films comprises the steps of imparting semiconductor properties to passivating or dielectric thin films from volatile precursory species produced from organosilicon polymer compounds.
Yang et al. (Yang, Lixin; Chen, Changqing; Ren, Congxin; Yan, Jinlong; Chen, Xueliang, “Synthesis of SiC Using Ion Beam and PECVD”, International Conference on Solid-State and Integrated Circuit Technology Proceedings, pp. 811-814) present a process for producing silicon carbide thin films comprising the steps of conferring semiconductor properties to passivating or dielectric thin films from volatile precursory species produced from organosilicon polymeric compounds.